Method of press casting and means therefor



arch 11 1924. 1,485,751

c. J. HULT METHOD OF PRESS CASTING AND MEANS THEREFOR Filed April 22 1922 lmwwwwfi w. wmy a tit Patented Mar. 11, 1924.

UNITED STATES CARL J'OHAN HULT, OF STOCKHOIM, SWEDEN, ASSIGNOR T0 AKTIEBOLAGET SVIIEINSKA PRESGJUTERIED, OF STOCKHOLM, SWEDEN, A CORPORATION.

moi) or mass casrme Ann MEANS rnnanroa Application filed Apri122, 1922. Serial No. 556,081.

To all whom it may concern: Be it known that 1,,CARL JoHAN Hum", manufacturer, a subject of the King of 'Sweden, residing at 44, Rorstran'dsgatan,

Stockholm, Sweden, have invented certain new and usefullmprovements in Methods of Press Casting and Means Therefor, of which the following is'a specification.

In press casting, as is well known, it is not possible to press the molten metal'into the mould through the direct action of a press plunger, that is to say, while the plunger is in contact with the metal during the pressing operation. The high temperature of the metal has namely suchan' inadvantageous influence on the plunger that it cannot be made so as to be freely movable in the manner required,whilesimultaneousl maintaining the requisite close fit. Instea the method of actuating the metal with compressed air has been employed, but then another great disadvantage will be met with, which drawback consists in great quantities of the metal being oxidized and thereby contaminated to the detriment of the casting. Moreover, the com ressed air in most cases produces an ins cient pressure by reason of its elasticity, and makes an accurate control of the pressure difiicult.

The efiecting of the casting by means of a press plunger is, however, to be preferred under all circumstances, in that this not only offers a possibility of making the pressure powerful, but also facilitates an accurate control of the pressure.

The present inventionhas for its object to facilitate the actuating of the molten metal by the employment of a press plunger as an intermediary member for pressing the molten metal into the mould. According to the invention, this is taking lace by a liquid material enclosed, between t e pressing surface of the plunger and the-point where the molten metal is let out to be further pressed into the mould, said li uid material having the property of not oxldizing or otherwise injuring the metal. In other words, the method according to the invention is carried out so that, on the molten metal having been let out of the melting crucible in a quantity required for filling t e mould, the liquid materm] is being pressed against the metal with the aid of the press plunger- The apparatus used in carrying out the method in questionis so devised, according to the invention, that the press plunger will always assume such a position with respect to the point where the molten metal is let out, that from this place practically no heat can be transmitted to the plunger. Therefore, the packing and the friction surfaces thereof cannot be injured. The liquid material enclosed between the plunger and the metal then serves as an effective heat insulating means.

Besides, provisions have been made in the metal crucible to the elfect that the outlet opening of the crucible which is closed by means of a valve, that is to say the valve seat, cannot be injured by the high tem perature of the metal when the valve moves against its seat.

In the accompanying drawing, a vertical section is shown of an apparatus adapted for carrying out the method in question.

The apparatus principally consists in a furnace, in the upper portion of which is arranged a crucible 1 around which the heat required to melt the metal is generated in a suitable manner.

Arranged in the bottom of the cruclble is the outlet opening 2 which is closed by and connected for this movement with the plunger rod 10. The plunger rod is guided in the cross piece 13 and is pivotally con nected. with the lever 11 which is rotatable on the stud 12. Enclosed within the space on the inside of the plunger is a liquid material, preferably molten lead, or at any rate a material having properties such that on touching the metal, it will not cause any oxidization of the latter. From the space 6-the channel 8 leads out to the mould.

In casting the valve 3 is opened, the molten metal being then emptied through the outlet 2 of the crucible after which it remains on the liquid material (the lead) within the space6. On' the valve having again been closed, the plunger 9 isactuate by means of the lever 11 or any other sultable device, whereby the liquid materialunderneath the pl er is pressed forth through the space 6 thus driving the superposed molten metal out through the channel 8 into the mould. By means of the plunger, a pressure as powerful as may be required may be produced, and inasmuch as the pressure is acting without yielding or resiliency, the pressure may be accurately adjusted. Moreover, the plunger is' protected during the whole casting operation so "that it will not in the least be injured through the influence of the high temperature of the metal.

The arrangement whereby the outlet opening 2 or the valve seat is protected against the high temperature of the metal consists in the part 14 of the bottom of the crucible, which forms the valve seat, being made of carborundum or. a material containing carborundum as its main constituent. This material not only allows of the valve being ground therein with the highest degree of tightness, but the valve seat, as well as the valve, will remain practically uninjured, even after having been used for a very long period, which has been shown by practice, and the said parts retain the perfect fit required to keep the metal in the crucible or to prevent its pressing back therein.

What I'claim as new and desire to secure by Letters Patent of the United States is 1. A method of pressure casting consisting in interposing between the molten casting metal and the pressure medium, a substantial insulating molten material which remains at a lower temperature during the casting operation than the casting metal so as to protect the pressure medium against the high temperature of the casting metal.

2. An apparatus for carrying out the methods set forth in claim 1 comprising a furnace including a body, a substantially U-shaped channel in the body, a crucible formed at the upper end of one side portion of the channel for-melting the casting metal, a valve seat of carborundum at the bottom of the crucible, a valve for coacting with the seat the lower medial portion of the channel receiving the insulating material, a branch leading from the channel adjacent the crucible through which molten casting metal is forced to a point remote from the furnace and a piston head operating in the other side portion of the channel, substantially as and for the purposes set forth.

In testimony whereof I afiix my signature in presence of two witnesses.

CARL J OHAN HULT. 

